(03-07-08) Leukocyte numbers and function in subjects eating n-3 enriched foods: selective depression of natural killer cell levels1-3.

Mukaro VR, Costabile M, Murphy K, Hii CS, Howe PR, Ferrante A.
ABSTRACT: INTRODUCTION: While consumption of omega-3 long chain polyunsaturated fatty acids (n-3 LCPUFA) has been recommended for those at risk of inflammatory disease such as rheumatoid arthritis (RA), the mechanism of their anti-inflammatory effect remains to be clearly defined, particularly in relation to the dose and type of n-3 LCPUFA. The objective of this study was to determine whether varying the levels of n-3 LCPUFA in erythrocyte membrane lipids, following dietary supplementation, is associated with altered numbers and function of circulating leukocytes conducive with protection against inflammation. METHODS: In a double-blind and placebo-controlled study, 44 healthy subjects aged 23-63 years consumed either standard or n-3 LCPUFA-enriched versions of typical processed foods, the latter allowing a target daily consumption of one gram n-3 LCPUFA. After six months, peripheral blood leukocyte and subpopulation proportions and numbers were assessed by flow cytometry. Leukocytes were also examined for lymphoproliferation and cytokine production, neutrophil chemotaxis, chemokinesis, bactericidal, adherence and iodination activity. Erythrocytes were analysed for fatty acid content. RESULTS: Erythrocyte n-3 LCPUFA levels were higher and absolute leukocyte and lymphocyte numbers were lower in subjects consuming n-3 enriched foods than in controls. There were no changes in the number of neutrophils, monocytes, T cells (CD3+), T cell subsets (CD4+, CD8+) and B cells (CD19+). However, natural killer (NK) (CD3-CD16+CD56+) cell numbers were lower in n-3 supplemented subjects than in controls and were inversely related to the amount of eicosapentaenoic acid (EPA) or docosahexaenoic acid (DHA) in erythrocytes. No significant correlations were found with respect to lymphocyte lymphoproliferation and production of IFN-g and IL-2, but lymphotoxin production was higher with greater n-3 LCPUFA membrane content. Similarly neutrophil chemotaxis, chemokinesis, bactericidal activity and adherence did not vary with changes in erythrocyte n-3 LCPUFA levels, but the iodination reaction was reduced with higher n-3 LCPUFA content. CONCLUSIONS: The data show that regular long-term consumption of n-3 enriched foods leads to lower NK cell numbers and neutrophil iodination activity but higher lymphotoxin production by lymphocytes. These changes are consistent with decreased inflammatory reaction and tissue damage seen in patients with inflammatory disorders receiving n-3 LCPUFA supplementation.

Source: Arthritis Res Ther. 2008 May 14;10(3):R57

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